Five clones of giant type bermudagrass, Cynodon dactylon (L.) pers. vars. aridus and afghanicus Harlan et de Wet, progenies from crosses among those five, and crossed, selfed, and open pollination progeny from selected F₁ plants were evaluated for response to simazine (2-chloro-4,6-bis(ethylamino)-s-triazine). The first two generations were also evaluated for their response to ametryn (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine). Two techniques were used. Culm cuttings, rooted in wet vermiculite, were placed into test tubes of simazine or ametryn suspensions at various concentrations or water. Culms were rated (1 to 9, 9 normal, 1 dead) for herbicide injury. Seeds were placed into petri dishes on moist filter paper, germinated in a germinator (day 35C, night 21C) and treated with 8ppm simazine or water in a greenhouse. Seedlings were rated visually for herbicide injury (7 normal, 5 affected, 1 dead) weekly, later daily, until a final drying and weighing of seedlings after all those in simazine were dead. Tolerance of all treated materials was expressed as percentage of control. There were significant differences among plants in tolerance to simazine with significance up to .001, although there was great variance within genotypes affected. The correlation between ametryn and simazine reaction was low. Tolerance scores were affected by condition of culms (significance .05), dosage, and nutrient levels. The clone by nutrient level interaction was significant at .01. Tolerance to simazine varied widely (more than 60%) among progeny of any plant as maternal parent. Progeny of reciprocal crosses between resistant and susceptible clones had similar (45 to 46) mean tolerance scores intermediate between parental scores indicating no dominance. Plants with the same cytoplasm ranged from most resistant (88%) to most susceptible (11%). Maternal effect on tolerance appears absent. The range of response for progeny of parents of any tolerance level indicates several pairs of genes are involved. Open pollination seedlings from consistently resistant plants averaged more resistant than seedlings from consistently susceptible plants. Giant bermudagrass simazine tolerance must be quantitatively inherited, possibly additive, with penetrance varying with plant condition, dosage, and other environmental constraints.

The impact of adjuvants on atomization and patternation of spray mixtures was evaluated. The data showed that certain adjuvants, in particular drift control agents, could potentially detrimentally affect the distribution of herbicide dose across the sprayed swath. The present research sets out to evaluate the impact of this distribution and to seek ways of improving the way researchers and users characterize and possibly mitigate these effects with a view to minimizing the potential detriments and maximizing the efficiency of herbicide active ingredient (AI) utilization. Different formulations of glyphosate with and without a novel polymeric drift control agent (AgRho DR 2000) applied to contrasting broad-leaved and grass weeds were used to evaluate several effects of polymer use. Variables included nozzle type (XR TeeJet extended range flat spray tips, TT Turbo TeeJet wide angle flat spray tips, and TurboDrop air induction nozzles) sampling position (principally under the nozzle centers and under the overlap between two adjacent nozzles), boom height (30, 45, and 60 cm above the target), spray delivery (the volume of spray arriving at the target), spray retention ( the volume of spray actually retained by the target foliage), and herbicide efficacy ( the response of the target weeds to the herbicide dose applied). The data showed that when the polymer was included in the spray mixture, the nozzle used, boom height, presence of the adjuvant, sampling position and certain interactions between these variables were all significant. Spray retention was affected by plant type and retention of coarse sprays was improved by the inclusion of DR 2000. Very coarse sprays reduced glyphosate efficacy on both grasses and broad-leaved weeds although that effect was reduced by use of DR. Addition of drift control agents always ii resulted in increased variability in spray distribution with concomitant increases in both retention and efficacy variability. Variability was shown to decrease with decreasing boom height. There was little correlation between spray delivery and herbicide efficacy. Deposit structure was shown to be a highly important factor in understanding herbicide dose transfer. A novel methodology utilizing digital imaging technology and diversity statistics was developed and evaluated to improve the way we measure and characterize deposit structures. Separation of qualitatively different treatments with similar volumetric distributions was possible. This methodology will be of use to both biologists and fOnTIulation chemists for prediction or explanation of biological results relating to deposit structure. Use of Scanning electron microscopy, and epi-fluorescence microscopy was used to characterize deposit morphology. Differences in deposit morphology were observed and documented leading to a possible explanation for the enhanced glyphosate activity in the presence of DR 2000 iii

No description available.

The aim of this work was to study the effect of the herbicide, 2,4-D on a mono- cot (Lolium temulentum Linn.) and a dicot (Raphanus sativus Linn.) in relation to drought stress, in order to elucidate if the combined treatments altered the survival of the plants. Herbicide effects were investigated on a number of plant developmental stages; germination, seedling growth, mature leaves and root function, and were combined with various water stress regimes.2,4-D did not alter the germination percentage in either species when applied singly or with polyethylene glycol (PEG) induce water stress. However, rate of seedling emergence and accumulation of chlorophyll, protein and proline were inhibited. Foliar application of 2,4-D at selective concentrations showed that in addition to induced growth distortion the herbicide reduced the survivial capacity of radish but enhanced that of rye grass to later drought stress. Analysis of the content of proline (a stress metabolite) in both species indicated that the accumulation of this compound was reduced in radish but enhanced in rye grass. In contrast, when 2,4-,VJ)&^Dlapplied via the roots, from water culture, the selectivity of effect was lost since proline accumulation was reduced in both species. Use of (^14)C-2,4-D showed that the herbicide remained in the roots when applied in water culture and that since a major response was seen in the roots this implied that some signalling was occuring between the two organs. From the results it would appear that the use of low doses of herbicides such as 2,4-D may be valuable in protecting certain plants from drought stress, whilst the susceptability of other plants could be increased hence making the herbicide more effective at low concentrations.

A method was developed for rapid plant regeneration from protoplasts of birdsfoot trefoil (Lotus corniculatus cv. Leo) using in vitro cotyledons and a new enzyme formula. Protoplasts of a transgenic Nicotiana tabacum cv. Xanthi line KCR were isolated from leaves, in vitro shoots, and calli by an enzyme formula consisting of 0.5 % Cellulase R-10 and 0.05 % Pectolyase Y23 with either 0.4 M sucrose or 0.5 M mannitol as the osmoticum. Nine asymmetric fusion experiments were conducted between iodoacetate inactivated birdsfoot trefoil and irradiated transgenic tobacco protoplasts. The fusion products underwent several divisions but no visible colonies were obtained. Resistance analyses revealed the inactivation of the herbicide resistant gene in the transgenic tobacco calli. A putative chlorsulfuron resistant line has been obtained by in vitro selection from birdsfoot trefoil cotyledonous protoplasts. Their regenerants had normal ploidy, and expressed improved tolerance when sprayed with chlorsulfuron at the rate of 30 g/ha.

[Abstract]Water quality in Australia’s northern grains farming areas often exceeds water quality trigger values for suspended sediments, nutrients and some herbicides (CBWC, 1999). While there are many land uses in these areas that contribute to the resultant water quality, of particular concern for the grains farming industry is the widespread detection in rivers of chemicals used by their industry, namely atrazine and metolachlor. A comparison of Hodgson Creek catchment (South East Queensland, Australia) herbicide data with national water quality guidelines shows that trigger values are frequently exceeded. That water quality trigger values are exceeded is expected for a highly modified catchment such as Hodgson Creek, and the Australian New Zealand Environment and Conservation Council (ANZECC) (2000) guidelines make provision that in such catchments, locally derived targets should be set. Natural resource managers therefore require skills in linking planned management with their ability to set or meet targets. The opportunity suggested itself for using catchment modelling to set realistic targets for water quality based on the adoption of best management farming practices. This study investigated the suitability of the Soil and Water Assessment Tool (SWAT) to fulfil this modelling role in an Australian context of land use management. To test the suitability of SWAT to fulfil this role, the study aimed to determine the feasibility of using the model to explicitly depict farm management practices at a paddock scale to estimate resultant catchment water quality outcomes. SWAT operates as two distinct sub-models. A hydrologic response unit (HRU) (the paddock scale model) generates runoff and constituents, and the output of many HRU are summed and routed through a stream network. The method for calibration of SWAT proposed in the user manual (Neitsch et al., 2001) is to calibrate against streamflow before calibrating sediment and then herbicides. The logic of testing in a process dependent order is sensible, however the method proposed by Neitsch et al. (2001) assumes that the HRU processes are reliable and calibration only need consider catchment scale processes. A review of the literature suggested that there had been limited testing of HRU process in studies where SWAT had been applied. Data available for model testing came from both paddock and catchment studies. The effects of cultivation management practices on runoff and erosion have been well characterised for the study area by Freebairn and Wockner (1996). Atrazine dissipation in soil and loss in runoff was available from a study of a commercial farm in the Hodgson Creek catchment (Rattray et al, 2007). An ambient and event based water quality monitoring for suspended sediments and herbicides provided data for the Hodgson Creek catchment for the period 1999 to 2004 (Rattray, unpublished data). The model required minimal calibration to achieve good predictions of crop yields and surface cover for winter crops. However, testing of summer cropping component revealed structural problems in SWAT associated with the end of a calendar year. Testing also revealed that perennial pastures and trees are modelled with unrealistic fluctuations in biomass and leaf area index. The model was able to represent hydrology well across a range of scales (1-50,000 ha). Catchment scale runoff data was well matched for a range of tillage treatments. The model was found to be able to attain a good prediction of monthly runoff at the catchment scale. This is consistent with the finding of most other SWAT studies. The model was able to represent average annual erosion reasonably well using the Universal Soil Loss Equation (USLE) when tested at the HRU scale (1 ha) against a range of tillage management data. When tested at the catchment scale the model was found to be able to match average annual sediment loads for the catchment however annual variability in sediment loads was poorly matched. Testing of the herbicide model for SWAT found that model compared poorly with paddock scale trial data. The reason for poor model performance can be attributed to an inadequate representation of processes and model output was unrealistic compared to our understanding of herbicide transport processes. When the model was tested at a catchment scale it was found to compare very poorly with catchment scale observations. This can be explained in part by the deficiencies of the HRU herbicide model, but is also due in part to difficulties in parameterisation of spatial and temporal inputs at the catchment scale. While SWAT provides a model with detailed physical processes, the capacity to apply the model is let down by an ability to practically determine the spatial and temporal extent of the farming practices (i.e. where and when are tillage and herbicides applied in the catchment). The challenge to applying SWAT is that farming practices in Australia vary markedly from year to year. SWAT requires the user to input crop practices in as a fixed rotation while Australia’s highly variable climate with unreliable seasonal weather patterns results in opportunistic farming practices. Hence this is a major limitation in the models ability to predict catchment outcomes, particularly for herbicides where off site losses are highly dependant on application timing. In attempting to validate herbicide losses at the whole of catchment scale it became apparent that uncertainty in the temporal variation of farm operations within the catchment poses a major limitation to accurately reproducing observations at the catchment outlet. It is concluded that that there is limited usefulness of SWAT for investigating the impacts of land management on catchment scale herbicide transport for Australian conditions.

Bibliography: leaves 151-172. / vii, 172 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied and Molecular Ecology, 2000?

Bibliography: leaves 126-143. / x, 143 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Adelaide University, Dept. of Applied and Molecular Ecology, 2001

Thesis (Ph. D.)--University of Adelaide, 1993. / Includes bibliographical references (leaves 203-220).

Thesis (Ph. D.)--University of Adelaide, Dept. of Crop Protection, 1996? / Includes bibliographical references (leaves 159-184).